Stencil sheet



45 I It is an object of the invention to provide Patented Nov; I 17, 19 25.

UNITED. STATES. PATENT. .oFF cE.

' :roHN' noUGnAss GRANGE, or B ooxFIELn, ILLINOIS, ASSIGNOR To WESTERN ELEcv TRIO COMPANY, r conrona'rnnyor NEW YQRK,'I\T. Y., A co roEATIoN OF Ew YORK.

No Drawing.

To all whom it may concern:

Be it known that I, JOHN DOUGLAS-S- cise, and exact description.

' stencil it is moistened for a period suflicient This invention relates to improvement in stencil sheets 'of the so-called dry type which comprise a sheet of fibrous material impregnated with a substance'which' is im perviousto ink, the stencil being formedby expressing the impregnating substance to expose the fibrous sheet, thus permitting the passage of the ink through the exposed portions of the sheet. Another type of stencil sheet known as the ,wet type is made by impregnating a thin lacerlikepaper. such as Japanese Yoshino paper with a protein such as gelatine which has been hardened with alum. Before the sheet is cut to form a cutting instrument perforates the base sheet, the ink passing through the perforations instead of through. the base sheet itself as in the case of the dry stencil. 'Both of these types of stencils are well known and a type of dry stencil which has been-'used rather extensively; is 'made'" by coating Yoshino paper with a-compound consisting essentially of gelatine-zcoagulated with a chronicagent such as potassium di-chromate In making a stencil of this sort in order to coagulate the gelatine the impregnating sheet must be exposed to light as the coagulating action of potassium di-chromate is dependent upon a light reaction which consumes. considerable time. In order to expose sten-" cilsmade in accordance with this process so that their entire surface is acted upon .by.

' light requires a large amount of floor-space when they are manufactured in anyquan j tity.

a dry type, of stencil and a method of nomical, rapid, and utilizes a minimum of apparatus and equipment. v I

' In carrying out my invention, I use as an impregnating compound for the fibrous sheet, a solution of gelatin, sugar, glycerine,

s ENcIL SHEET.

Application filed November 24,1922. Serial No. 603,125.

pared, the salt being dissolved in'the water,

and this solution added to the mixture above described." The resulting mixture is thenfiltered by any suitable means. The fibrous sheets to'be'impregnated, which are'pref-' erably of an open, lace-like material such.-

place, the aluminum salt causes a-hardening of the impregnating, compound, so-that the as Japanese Yoshino paper, are then taken resulting stencil sheet is. to a considerable extentinsoluble ,in water and will not soften under the lnfluence of moisture to an extent that will affect its satisfactory use.

The impregnating mixture wh'ch I have fou'nd'to bethe'best-contains ingredients in the following proportions:

- a Parts by weight.

may be varied within reasonable limits andproduce a satisfactory stencil, exceptv thatthe aluminum sulphate "or other aluminum salt, such as a'mmoniumor potassium alum, shouldbe in an amount not less than .22 of a part nor more than .Giofa part. If

salt'is employed, I find that the impregnating compound 'will not'be hard enough .less than .22 of a partof'the aluminum to resist the heat of summer sufliciently to. I plermitdtssuccessful use'at this season. On I:

the otherhand, if morethan .6 of a part of the aluminum salt isemployed, I find that the'impregnating solution forms a coating having a porous and, cellularlikestru'cture which will produce. unsatisfactory stencil sheets, since they permitthe passage of inkp through portions of the coating where it is not desired. I attribute the success I have had with stencils impregnated"with the compound above described, to a large extent, to my discovery of the limits within wlnclrthe amount of aluminum salt must be maintained. If potassium alum or ammonium alum are maintained within the v limits above given satisfactory stenclls may be made using either of these materials, but I have found'after long experiments that aluminum sulphate produces the better stenoil. The aluminum sulphate is more desirable in that it produces a harder and tougher coating, which at the same time is not brittle.

The acetic acid in the composition serves to retardsthe hardening action of the aluminum salt on the gelatine until the acetic acid is volatilized. as the stencil sheet drys. Were the acetic acid not present it would be impossible to keep the compound sufficiently fluid to impregnate the stencil sheets as they are subjected to it.

- acetic acid is especially necessary where an aluminum salt is used as the hardening agent, since its hardening action is not dependent on light (as is the coagulating action of potassium di-chromate) but will act immediately to harden the gelatine unless retarded. i 7

The glycerine is a tempering agent. The stencil sheet after being impregnated with the compound is kept in a flexible condi- Y coloring material utilized maybe of any suitable type. I find it preferable, however, to use an acid dye or some other material which will form a lake with the aluminum salt, so that upon moistening the stencil sheet preparatory to making the stencil, the coloring material will not run.

By employing aluminum sulphate or other aluminum salts as the hardeningagent, it is unnecessary to subject the stencil to light while drying, so, that as a consequence the impregnated stencils may be stacked closely together, as for instance, on suitable wooden frames which may be placedvin suitable drying chambers. In vthis way a large number of stencils may be dried within a small compass and the drying operation rapidly achieved; whereas if a chromic coagulating agent is utilized,

it is necessary to separate the stencils sufv ficiently to permit their surfaces to come into contact with the light to secure the requisite'coagulation. As a consequence, in the manufacture of stencils using a chromic The coagulating agent, it has been found neces: sary to utilize large enclosures having great expanses of glass in order to produce stencil sheets on a large scale. r

Where stencils are made in accordance with my invention, the moisture content and temperature of the air in which the impregs nated sheets are dried are the factors controlling the speed at which the stencil sheets may be made. Where I have impregnated the tissue sheets with my compound and dried them in an enclosure maintained approximately 95 Fahrenheit, I have been able to make stencil sheets ready for use within from one to two hours. with the use of an enclosed drying chamber having suitable humidity controlled equipment and means for providing proper circulation of the humidified and heated air, thetime necessary to produce stencils in accordance with my invention may undoubtedly' be materially reduced.

However,

On the other hand, where stencils are made using a protein coagulated with. a chromic coagulating agent, since light is the factor controlling the coagulation of the impregnating substance, stencils cannot be made in less than six hours, and under unfavorable light conditions may. require 12 hours to complete their fabrication.

What is claimed is: 1. A stencil blank capable of being stencilized, comprising a sheet of fibrous material impregnated with a compound includmg a protein, an aluminum salt, an agent to retard the hardening effect of the alumi- 7 colormg material and water.

num salt a suitable tempering agent, a

cilized, comprising a sheet of fibrous material impregnated with a compound including a protein, aluminum sulphate, an agent to retard the hardening eflect of the aluminum sulphate, a suitable tempering agent, a coloring material and water.

3. A stencil blank capable of being stencilized, comprising a sheet of fibrous material impregnated with a compound including a protein, a single aluminum salt, an agent to retard the hardening eifect of the aluminum salt, a tempering agent, a coloring material and water.

4. A stencil blank capable of being stencilized, comprising a sheet of fibrous material impregnated with a compound consisting es sentially of a protein, a single aluminum salt, a volatile agent to retard the hardening effect of the aluminum salt, asuitable tempering agent, a coloring material and water.

5. A stencil blank capable of being stencilized, comprising a sheet of fibrous material impregnated with acompound consisting es- 6. A stencil blank capable of being stencilized, comprising a sheet of fibrous material impregnated with a compound consisting essentially of gelatin, acetic acid, a single aluminum salt, a tempering agent, a coloring material and water.

7. A stencil blank capable of being stencilized, comprising a sheet of fibrous material impregnated with a compound consisting essentially of a protein, an aluminum salt, an agent to retard the hardening effect of the aluminum salt, a tempering agent, a coloring material and water, the aluminum salt being in the ratio of not less than 1.75 parts by weight to 100 parts by weight of protein.

8. A stencil blank capable of being stencilized, comprising a sheet of fibrous material impregnated with a compound consisting essentially of a protein, an aluminum salt, an agent to retard the hardening efiect of the aluminum salt, a tempering agent, acoloring material and water, the aluminum salt being in the ratio of not more than 4.7 5

parts by weight to 100 parts by weight of protein.

9. A stencil blank capable of being stencilized, comprising a sheet of fibrous material impregnated with a compound consisting essentially of a protein, an aluminum salt, an agent to retard the hardening effect of the aluminum salt, a tempering agent, a coloring material and water, the aluminum salt being in the ratio of not less than 1.7 5 parts nor more than 4.7 5 parts by weight to 100 parts by Weight of protein.

10. A stencil blank capable of being stencilized, comprising a sheet of fibrous material impregnated with a compound consisting of a protein, aluminum sulphate in the ratio of 100 parts of protein to not less than 1.75 parts nor more than 4.75 parts by weight of the aluminum sulphate, an agent to retard the hardening effect of the aluminum sulphate, a suitable tempering agent, a coloring material and water.

11. A stencil blank capable of being stencilized, comprising a sheet of fibrous material impregnated with a compound consisting of sugar, acetic acid, glycerine, gelatine, aluminum sulphate, and water.

12. A stencil blank capable of being stencilized, comprising a sheet of fibrous ma terial impregnated with a compound consisting of sugar about 5.7 parts, acetic acid about 5.5 parts, glycerine 14' parts, gelatine about 12.6 parts, water about 60.7 parts, and aluminum salts not less than .22 of a part nor more than .6 of apart.

13. A stencil blank capable of being stencilized, comprising a sheet of fibrous material impregnated with a compound consisting of gelatine about 12.6 parts, sugar about 5.7 parts, acetic acid about 5.5 parts, glycerinc about lt parts, coloring material about 1.2 parts, and aluminum salts not less than .22 of a part nor more than .6 of a part.

14. A stencil blank capable of being stencilized, comprising a sheet of fibrous ma terial impregnated Witha compound consisting of sugar about 5.7 parts, acetic acid about 5.5 parts, glycerine about 14 parts, gelatine about 12.6 parts, Water about 60.7

parts, coloring material about 1.2 parts, and

JOHN DOUGLASS GRANGE. 

